Class UID

A UID represents an identifier that is unique over time
with respect to the host it is generated on, or one of 216
"well-known" identifiers.

The UID() constructor can be used to generate an
identifier that is unique over time with respect to the host it is
generated on. The UID(short) constructor can be used to
create one of 216 well-known identifiers.

A UID instance contains three primitive values:

unique, an int that uniquely identifies
the VM that this UID was generated in, with respect to its
host and at the time represented by the time value (an
example implementation of the unique value would be a
process identifier),
or zero for a well-known UID

time, a long equal to a time (as returned
by System.currentTimeMillis()) at which the VM that this
UID was generated in was alive,
or zero for a well-known UID

count, a short to distinguish
UIDs generated in the same VM with the same
time value

An independently generated UID instance is unique
over time with respect to the host it is generated on as long as
the host requires more than one millisecond to reboot and its system
clock is never set backward. A globally unique identifier can be
constructed by pairing a UID instance with a unique host
identifier, such as an IP address.

read

Constructs and returns a new UID instance by
unmarshalling a binary representation from an
DataInput instance.

Specifically, this method first invokes the given stream's
DataInput.readInt() method to read a unique value,
then it invoke's the stream's
DataInput.readLong() method to read a time value,
then it invoke's the stream's
DataInput.readShort() method to read a count value,
and then it creates and returns a new UID instance
that contains the unique, time, and
count values that were read from the stream.